Node.js在第一次啓動時給出了不可預知的ajax響應

Question

我使用node.js作爲後端，canjs作爲前端庫。

節點代碼：

var express = require('express'); 
var app = express(); 
var http = require("http"); 
var fs = require("fs"); 
var cons = require('consolidate') 

app.configure(function(){ 
     app.engine('html', cons.handlebars); 
     app.set('view engine', 'html'); 
     app.set('views', __dirname) 
     app.use(express.favicon()) 
     app.use(express.logger('dev')) 
     app.use(express.static(__dirname)) 
     app.use(express.bodyParser()) 
     app.use(express.methodOverride()) 
     app.use(express.cookieParser("secret")) 
     app.use(express.session({ secret: 'keyboard cat' })) 
     app.use(app.router) 
    }); 

app.init = function(){ 
    fs.readFile('./sample.json', 'utf8', function(error, data) { 
     if (error) { 
      throw(error); 
     } 
     else 
      app.set("json", data); 
    })}; 

app.get('/things', function(req, res){ 
    app.init(); 
    res.set('Content-Type', 'text/json'); 
    res.send(app.get("json")); 
}); 

app.get('/things/:id', function(req, res){ 
    app.init(); 
    res.set('Content-Type', 'text/json'); 
    res.send((JSON.parse(app.get("json")))[req.param('id')]); 
}); 

app.get('/main.html', function(req, res){ 
    app.init(function(error, data){ 
     if (error) {throw error} 
     res.render('main.html'); 
    }); 
}); 

app.listen(3000); 

Can.js代碼：

Todo = can.Model({ 
    findAll: "GET /things", 
    findOne: "GET /things/{id}", 
},{}); 

$(document).ready(function(){ 

    Todo.findAll({}, function(todos){ 
     console.log(JSON.stringify(todos)); 
    }) 

    Todo.findOne({ id: 1 }, function(todo) { 
     console.log(todo); 
    }) 

}); 

HTML：

<script type="text/javascript" charset="utf-8" src="./jquery-1.8.2.js"></script> 
<script type="text/javascript" charset="utf-8" src="./can.jquery-1.0.7.js"></script> 
<script type="text/javascript" charset="utf-8" src="./can.fixture.js"></script> 
<script type="text/javascript" charset="utf-8" src="./master.js"></script> 

JSON：

{"0":{"id":1,"name":"do the dishes"},"1":{"id":2,"name":"go to dentist"},"2":{"id":3,"name":"go swimming"},"4":{"id":5,"name":"masturbate"}} 

每次服務器啓動時，控制檯會發現這兩個函數返回未定義或500錯誤的AJAX GET響應（的findAll和findOne）：

XHR finished loading: "http://localhost:3000/things". jquery-1.8.2.js:8416 
undefined master.js:12 

GET http://localhost:3000/things/1 500 (Internal Server Error) jquery-1.8.2.js:8416 
XHR finished loading: "http://localhost:3000/things/1". jquery-1.8.2.js:8416 
Uncaught TypeError: Function.prototype.apply: Arguments list has wrong type 

但如果我刷新頁面在此之後，兩個功能將正常工作，給出：

XHR finished loading: "http://localhost:3000/things". jquery-1.8.2.js:8416 
{"0":{"id":1,"name":"do the dishes"},"1":{"id":2,"name":"go to dentist"},"2":{"id":3,"name":"go swimming"},"4":{"id":5,"name":"masturbate"},"length":0,"_namespace":".observe2"} master.js:12 
XHR finished loading: "http://localhost:3000/things/1". jquery-1.8.2.js:8416 
Constructor {name: "go to dentist", _data: Object, id: 2, _namespace: ".observe3"} 
master.js:16 

什麼是GOING？

Answer 1

的問題是，你打電話app.get("json");前的值已經由app.init的fs.readfile回調（這在第一次調用app.init();返回後的某個時候發生）設置。

您應該更改您的代碼只調用一次app.init，並且在其工作完成之前不要監聽請求。

app.init = function(callback){ 
    fs.readFile('./sample.json', 'utf8', function(error, data) { 
     if (error) { 
      throw(error); 
     } else { 
      app.set("json", data); 
      callback(); 
     } 
    }); 
}; 

... 

app.init(function() { 
    app.listen(3000); 
});